We were apart for a year, which felt like torture until I found this site and saw other people's stories of spending years and years apart. The longest we went without seeing each other was about 4 months - he visited me in the US twice for a couple of weeks and I visited him once. Like almost everyone else has said, one of the most important things for us was having our next visit planned before the current one was over, which isn't always possible, but if you're atleast able to have some kind of rough timeline figured out it makes a world of difference.
We met while I was living in the UK and we really started to plan the wedding only about 2 or 3 months after I had to move back to the US. Having something to plan and something to work towards is the most important thing, I think. I can't imagine what it would have been like to be apart with no end-date in sight.
We relied mostly on the phone, talking for at least an hour every day, which cost us an absolute fortune, but it was the only thing that really worked for us.
The last couple of months are the strangest, really. You start to feel yourself mentally distancing yourself from your life in the US because you're doing so much planning and thinking about moving to the UK. Also, I've heard a lot of people say that they fight much more right before they're about to see eachother, and we found that to be true sometimes as well. Stress,anticipation,and all kinds of emotions just take over. Also I think you get to a point where you've planned so much that you just don't really have anything else to do, but like someone else said, focus on spending time with your family and your friends and just doing things for yourself.
We never had any serious trust issues, but I don't think it's uncommon or terrible, especially in LDRs, where you have a lot of time to let your mind wander. I had moments of my own, but everyone does and you just have to be able to talk about anything that's bothering you.
It's all worth it, of course! Hang in there!